1. Field of the Invention
The present invention relates to an antenna and portable terminal apparatus suitable for use in, for example, a cellular phone.
2. Description of the Related Art
A cellular phone is provided with a whip antenna that can be extended from a box-shaped body during use and can be accommodated in the box-shaped body at non-use, and an internal antenna for exclusive use of receiving. As the whip antenna, a monopole antenna has been used, and as the internal antenna, an inverted-F antenna has been used. The inverted-F antenna can be integrated into the box-shaped body by bending a plate-shaped monopole antenna parallel to the bottom board (earth plate).
FIG. 10 is a view showing the structure of the conventional internal antenna. A helical antenna 103 shown in FIG. 10 is viewed from the side of the lower case 100 (the opposite side to the contact side with a human body). In FIG. 10, most portions on a base board 101 are covered with a shield case 102, and on the upper portion of the base board 101 that is not covered with the shield case 102, the helical antenna 103 is horizontally positioned with its feeding point and open end portion fixed on the base board 101.
The above-mentioned conventional whip antenna, however, uses the box-shaped body as the bottom board; accordingly, it is disadvantageously affected by a peripheral mounted thereon. The inverted-F antenna disadvantageously occupies a large space of the box-shaped body because of being a plate shape. In the conventional internal antenna as shown in FIG. 10, the helical antenna 103 is horizontally positioned on the base board 101; therefore, it occupies a larger area for installation on the base board, while decreasing the area for installation of the other components on the base board. Further, since the helical antenna 103 is horizontally positioned on the base board 101 and the open end portion is fixed on the base board, in the conventional antenna, it is impossible to use the back side of the base board, thereby to lose a space for placing the bottom board between the open end portion and a human body. Therefore, it is easily affected by a human body disadvantageously.
In the case of using a chip antenna such as a microstrip antenna as an internal antenna, it occupies a reduced amount of space because of being miniaturized. However, since the whole chip is mounted on the base board, hence to decrease the space for installation of the other components on the base board, it is also impossible to place the bottom board between the open end portion and a human body. Therefore it is easily affected by a human body disadvantageously.
It is an object of the present invention to provide an antenna and portable terminal apparatus that occupies a reduced amount of space for its installation on a base board and that is not affected much by an approach of a human body, by using a helical antenna from a feeding point of a quarter wave antenna to a portion of one-eighth wavelength and a bent antenna from the portion of one-eighth wavelength to an open end portion.
An antenna according to the present invention comprises a helical antenna portion having one end connected to a feeding point of said antenna apparatus and having a length corresponding to substantially half of an electrical wave length of said antenna apparatus, and an extended antenna portion having one end connected to the other end of said helical antenna portion and having a length corresponding to substantially half of an electrical wave length of said antenna apparatus, said extended antenna portion being bent at least at one portion.
A portable terminal apparatus according to the present invention comprises a helical antenna portion having one end connected to a feeding point of said antenna apparatus and having a length corresponding to substantially half of an electrical wave length of said antenna apparatus, and
an extended antenna portion having one end connected to the other end of said helical antenna portion and having a length corresponding to substantially half of an electrical wave length of said antenna apparatus, said extended antenna portion being bent at least at one portion.